JP4847472B2 - Artificial leather base material and artificial leather using the base material - Google Patents

Description

  The present invention relates to a base material for artificial leather. Using this artificial leather base material, it has a very dense and elegant appearance of raised hair, and has excellent color development, but also has excellent surface wear durability such as pilling resistance, and is soft and swollen. Napped-toned artificial leather that combines a texture with a texture, and a silver-faced artificial leather that has a high smoothness and fine crease surface, combined with a high adhesive peel strength and a soft and bulging texture Can be manufactured.

  Conventionally, napped artificial leathers such as suede artificial leather and nubuck artificial leather having napped fibers formed on the surface of a substrate composed of fiber bundles and a polymer elastic body are known. Napped-toned artificial leather is required in terms of sensibility such as appearance (surface feeling closer to that of natural leather), texture (combined soft touch with appropriate swelling and fullness), and color development (color clarity and density). In addition, it is required to satisfy all of the requirements in terms of physical properties such as light resistance, pilling resistance, and wear resistance at a high level, and various proposals have been made to solve this.

  In order to satisfy the requirements in appearance and texture, for example, a method of making the fibers constituting the artificial leather into ultrafine fibers is generally used. As a method of manufacturing artificial leather made of ultrafine fibers, a method of splitting composite fibers such as sea-island type and multi-layer laminated type, or transforming them into ultrafine fiber bundles by decomposing or extracting one component is widely adopted. ing. Napped-toned artificial leather and silver-faced artificial leather using a base material for artificial leather in which a polymer elastic body is incorporated into a nonwoven fabric composed of ultrafine fiber bundles obtained from the composite fibers are very highly evaluated in appearance and texture. It has gained. However, as the fineness is reduced, there is a drawback that the color developability is lowered and the vividness and density are remarkably inferior, and particularly in the napped artificial leather, the high quality requirements are satisfied. Absent.

  As a method for producing a nonwoven fabric structure used for a base material for artificial leather, a spun fiber is cut into a length of 100 mm or less to form staple fibers, and this is a nonwoven web having a desired basis weight by a card method or a papermaking method. In general, a method in which a plurality of nonwoven webs are stacked as necessary, and then fibers are entangled by a needle punch method, a spunlace method, or the like. A base material for artificial leather is produced from a nonwoven fabric structure having a desired bulkiness and entanglement degree produced by these methods. The napped-tone artificial leather and the silver-tone artificial leather using such an artificial leather base material are highly evaluated particularly in terms of texture. However, the staple fibers constituting the nonwoven fabric structure are fixed in the base material by the entanglement between the fibers and the contained polymer elastic body, but the raised surfaces of the napped artificial leather or the silver artificial leather Since the fiber length is short at the adhesive interface with the silver surface layer, the tendency to be pulled out from the nonwoven fabric structure or fall off is inevitable. Due to this tendency, important surface properties such as friction durability of the napped surface and adhesive peel strength of the silver surface layer are lowered. In order to solve this problem, for example, a general method is to increase the degree of entanglement of the nonwoven fabric structure, to bond the fibers together, or to contain a large amount of a polymer elastic body to strongly restrain the fibers. Has been adopted. However, when the degree of entanglement is increased or the content of the polymer elastic body is increased, on the other hand, the texture of the artificial leather is remarkably deteriorated, and it is difficult to satisfy the appearance, texture and surface properties at the same time.

  For improvement of surface friction durability represented by pilling resistance of napped fibers in napped-toned artificial leather, for example, needle punch entanglement made of sea-island type fibers that generate ultrafine fiber bundles made of ultrafine fibers of 0.8 denier or less The nonwoven fabric is immersed in an aqueous solution of polyvinyl alcohol (hereinafter sometimes abbreviated as PVA) and dried to temporarily fix the shape of the nonwoven fabric; the sea component is extracted and removed with an organic solvent that dissolves the sea component of the sea-island fiber. Suede-like artificial leather obtained by impregnating and coagulating a dimethylformamide (hereinafter sometimes abbreviated as DMF) solution of polyurethane; and raising the surface is proposed (see Patent Document 1). It has been proposed to add coarse particles having a diameter larger than one-fourth of the fiber diameter and inert to the fibers in the ultrafine fiber.

  In Patent Document 2, a needle punch entangled non-woven fabric made of sea-island fibers is impregnated with a polyurethane DMF solution and solidified, and then a leather-like base material obtained by extracting and removing sea components is raised to produce a suede-like artificial fabric. Manufactures leather. The fiber bundle constituting the substrate has a fine fiber (A) of 0.02 to 0.2 denier and a fineness of 1/5 or less of the average fineness of the fine fiber (A) and less than 0.02 denier. And the ratio of the number (A / B) is 2/1 to 2/3. The fiber bundle contains substantially no polymer elastic body, and the ratio (A / B) of the number of fine fibers (A) and extra fine fibers (B) in the napped fibers is 3/1 or more. .

  In addition, a method has been proposed for improving the pilling resistance of a suede-like artificial leather by dissolving a part of the polymer elastic body existing at the root of the napped fiber with a solvent and fixing the root of the napped fiber. (See Patent Document 3).

In Patent Document 4, in order to obtain a long-fiber non-woven fabric that can be converted to a fine-surface-touch nubuck-like artificial leather, the long fibers are actively cut when they are entangled with a needle punch. It has been proposed to develop cut ends of fibers of ˜100 pieces / mm ² to eliminate distortion caused by the characteristic entanglement treatment in the long-fiber nonwoven fabric. Moreover, in an arbitrary cross section parallel to the thickness direction of the nonwoven fabric, fiber bundles are present in the range of 5 to 70 per 1 cm in width (that is, oriented in the thickness direction by needle punching in an arbitrary cross section parallel to the thickness direction of the nonwoven fabric. The total area occupied by the fiber bundle is 5 to 70% of the cross-sectional area in any cross section orthogonal to the thickness direction of the nonwoven fabric. Propose to be.

Patent Document 5 is composed of long fibers that can be converted into ultrafine fibers of 0.5 de or less, the degree of crimp of the long fibers is 10% or less, and the fiber density of the nonwoven fabric is 0.25 to 0.50 g / A long fiber entangled nonwoven fabric of cm ³ is proposed.

However, in the method described in Patent Document 1, since the sea component of the sea-island fiber is extracted and removed, the polyurethane is infiltrated and solidified with a DMF solution of polyurethane, so that polyurethane penetrates into the ultrafine fiber bundle and avoids hardening of the texture. I can't. In addition, since coarse particles are added to the fiber, a soft texture and feel cannot be obtained.
In the method described in Patent Document 2, since the sea component of the sea-island fiber is extracted and removed, polyurethane is impregnated and solidified, so that polyurethane is not substantially present in the outer peripheral portion and inside of the ultrafine fiber bundle. It is possible to obtain a soft texture and feel. However, since the ultrafine fiber bundle is not fixed with polyurethane, the pilling resistance is insufficient.
In the method described in Patent Document 3, the effect of fixing fibers inside the leather-like base material is obtained simply by dissolving a part of the polymer elastic body existing on the outermost surface of the leather-like base material and fixing the roots of the napped fibers. Since the gripping ability of the polymer elastic body with respect to the fibers is low, a good pilling resistance improving effect cannot be obtained for fibers of 0.01 dtex or more.
In the method for obtaining the long-fiber nonwoven fabric structure of Patent Document 4, the cut end is expressed so as not to reduce the physical properties as much as possible to a target level or less. However, as a matter of fact, a considerable number of long fibers are cut, so the effect of improving the non-woven fabric strength properties due to the continuity of the fibers, which is an advantage of long fibers, is significantly reduced, and the characteristics of long fibers are fully utilized. I can't. In addition, the entanglement treatment of Patent Document 4 is not for entanglement of long fibers with each other from the surface of the long fiber nonwoven fabric to the inside, and further across the opposite surface, but 5-100 pieces of the long fibers on the surface are cut evenly. This is done to create a very large number of cut edges of / mm ² . Accordingly, it is necessary to perform needle punching under conditions that are considerably stronger than those employed in general entanglement. Furthermore, since the fibers entangled to obtain the long fiber nonwoven fabric structure are extremely thick fibers of 2.8 denier or more as in the case of conventional short fibers, the long fibers cannot be sufficiently entangled and densified. It is difficult to obtain a high-quality nubuck-like artificial leather as intended by the present invention.
According to the method described in Patent Document 5, although the denseness can be improved, a polymer elastic material-containing artificial leather base material having a high fiber density and a soft texture cannot be obtained.

JP-A-53-34903 (pages 3 to 4) JP-A-7-173778 (pages 1 and 2) JP-A-57-154468 (pages 1 and 2) JP 2000-273769 A (pages 3 to 5) JP-A-11-200209 (pages 2 to 3)

  Conventionally, in napped-toned artificial leather, elegant and dense napping feeling and coloring of ultrafine fiber napping; soft swell and fullness; surface friction durability represented by soft surface touch and pilling resistance of ultrafine napping It was difficult to combine sex and the like. In silver-tone artificial leather, the balance between the silver surface part and the base material part, for example, it can express a sense of unity with a hard part that has high smoothness and can express a fine crease and a base material part with high flexibility. Balance of soft properties; texture of silver surface and base material with soft swell and fullness; represented by soft texture due to high flexibility of base material and adhesive peel strength at silver surface-substrate interface It was difficult to combine surface mechanical properties.

  The present invention provides a base material for artificial leather that combines the performance of the sensibility surface and the performance of the physical properties, both of which have conventionally been recognized as contradictory performances, in the artificial leather base material. It is to be. By using the base material of the present invention, it is possible to obtain an artificial leather that has both high quality and high physical properties that have not existed before.

Back Artificial leather obtained by the present invention has the above properties at a high level, so it is used for clothing represented by jackets, skirts, shirts and coats, and for footwear represented by sports shoes and women's shoes. , For apparel represented by belts, for bags represented by handbags and school bags, for furniture represented by sofas and office chairs, for seats and interior materials of vehicles represented by passenger cars and trains, aircraft and ships, It can be suitably used for sports gloves such as golf gloves, batting gloves, baseball gloves, driving gloves, and various gloves represented by work gloves.

As a result of intensive studies to achieve the above-mentioned problems, the present inventors have reached the present invention. That is, the present invention relates to a non-woven fabric structure composed of ultrafine fiber bundles and a base material for artificial leather composed of a polymer elastic body contained therein (1) to (4):
(1) The ultrafine fiber bundle is formed of an average of 6 to 150 converged ultrafine fibers,
(2) The cross-sectional area of the ultrafine fibers forming the ultrafine fiber bundle is 27 μm ² or less, and the cross-sectional area of 80% or more of the ultrafine fibers is in the range of 0.9 to 25 μm ² .
(3) The average cross-sectional area of the ultrafine fiber bundle is in the range of 15 to 150 μm ² , and (4) In any cross section parallel to the thickness direction of the nonwoven fabric structure, the cross section of the ultrafine fiber bundle has an average of 1000 to 1000 It is related with the base material for artificial leather characterized by satisfying simultaneously existing in the range of 3000 pieces / mm < ² >.

The present invention is further characterized in that the following steps are performed in the order of (a), (b), (c) and (d), or (a), (b), (d) and (c). The present invention relates to a method for producing a base material for artificial leather.
(A) Melting and spinning sea-island type fibers having an average number of islands of 6 to 150, an average cross-sectional area ratio between the sea and islands of 5:95 to 70:30, and an average cross-sectional area of 30 to 180 μm ² , and cutting this A process for producing a long fiber web by accumulating on a collecting surface in a random orientation state,
(B) A plurality of the above-mentioned long fiber webs are overlapped as necessary, and from both sides, needle punching is performed under the condition that at least one barb penetrates, and the sea-island type fibers are three-dimensionally entangled, A nonwoven fabric structure in which the cross-section of sea-island fibers is present in an average range of 600 to 4000 / mm ² in a cross-section parallel to the thickness direction by densification and / or fixation by shrinkage treatment or heat press treatment as necessary. Manufacturing process,
(C) impregnating the nonwoven fabric structure with a polymer elastic body solution and solidifying the polymer elastic body by a wet method; and (d) extracting a sea component polymer from the sea-island fibers constituting the nonwoven fabric structure or The process of removing by decomposing and transforming sea-island fibers into ultrafine fiber bundles.

  In the base material for artificial leather of the present invention, since the ultrafine fiber bundles are gathered in a dense state that has not existed in the past, a surface state with extremely high denseness and excellent smoothness can be obtained. Using the artificial leather base material of the present invention, it has a smooth and elegant appearance and touch that are not inferior to natural leather, and also has excellent surface friction durability such as coloring, swelling texture and pilling resistance. Napped artificial leather can be obtained. In addition, it is possible to obtain a silver-tone artificial leather that is smooth and inferior to natural leather, but has a soft and swell feel and excellent surface strength such as adhesive peel strength.

  The base material for artificial leather according to the present invention includes, for example, the following steps (a), (b), (c) and (d), or (a), (b), (d) and (c). It can be obtained by performing in order.

Step (a)
A sea component polymer and an island component polymer are extruded from a composite spinning die, and a sea island type fiber is melt-spun.
The composite spinning nozzle has an array of nozzle holes arranged in a straight line in parallel, in which any number of island component polymers can be dispersed in the range of 6 to 150 on average in the sea component polymer. A structure having a plurality of rows arranged in a shape is preferable.
Relative supply of sea component polymer and island component polymer so that the average area ratio (that is, polymer volume ratio) in the cross section of the resulting fiber is any ratio in the range of sea / island = 5/95 to 70/30 While the amount or supply pressure is adjusted, the die temperature is discharged from the die in a molten state under temperature conditions such that the die temperature is any temperature in the temperature range of 180 to 350 ° C.
The average cross-sectional area of the obtained sea-island fiber is any value in the range of 30 to 180 μm ² , and the average single fineness is, for example, if the island component polymer is nylon 6 and the sea component polymer is polyethylene, the composite polymer Depending on the area ratio, any value in the range of 0.3 to 1.8 dtex is preferable, and any value in the range of 0.5 to 1.7 dtex is more preferable. In the present invention, the long fiber is a fiber having a fiber length longer than a short fiber having a fiber length of usually about 3 to 80 mm, and means a fiber that is not intentionally cut like a short fiber. For example, the fiber length of the long fiber before ultrafinening is preferably 100 mm or more, and can be produced in a technical manner and has a fiber length of several meters, several hundreds of meters, several kilometers or more as long as it is not physically cut. Is also included.
The melt-spun sea-island fiber is accumulated in a collection surface such as a net in a random orientation state without being cut to produce a long fiber web having a desired basis weight (preferably 10 to 1000 g / m ² ). .

Step (b)
After laminating a plurality of the long fiber webs in the thickness direction using a cross wrapper as necessary, needle punching is performed under the condition that at least one barb penetrates from both sides simultaneously or alternately. Non-woven fabric structure in which sea-island type fibers are gathered very densely, in which sea-island type fibers exist at an average density in the range of 600 to 4000 pieces / mm ^{2 on} a cross-section parallel to the thickness direction in three dimensions. Get. An oil agent may be applied to the long fiber web at any stage after the production and until the entanglement treatment.
If necessary, the entangled state may be made denser by shrinking treatment such as introduction into warm water set at any temperature in the temperature range of 70 to 150 ° C. Moreover, the fibers may be gathered more densely by performing a heat press treatment, and the form of the nonwoven fabric structure may be fixed.
For example, if the island component polymer is nylon 6 and the sea component polymer is polyethylene, the average apparent density of the nonwoven fabric structure is preferably any value in the range of 0.1 to 0.6 g / cm ³ . The average apparent density is determined by a method that does not apply a load such as compression, for example, a method by cross-sectional observation with an electron microscope or the like. The basis weight of the nonwoven structure is usually 100 to 2000 g / m ² .

Step (c)
A non-woven fabric structure in which sea-island fibers are gathered very densely to a predetermined level is impregnated with a polymer elastic body solution, and the polymer elastic body is solidified by a wet method.

Step (d)
(D) The sea component polymer is removed from the sea-island fiber constituting the nonwoven structure by extraction or decomposition, and the sea-island fiber is transformed into an ultrafine fiber bundle.

About the base material for artificial leather obtained as described above, the following steps are further performed in the order of (e) and (f), or (f) and (e), and then as necessary ( By performing g), it is possible to obtain a napped-tone artificial leather having the effects of the present invention, such as a suede tone and a nubuck tone.
Step (e)
Forming napped fibers made of ultrafine fibers on at least one surface;
Step (f)
The process of dyeing.
Step (g)
The process of trimming ultrafine fiber napping.

Moreover, about the obtained base material for artificial leather, after performing a process (h), the silver surface tone artificial leather which has the effect of this invention can be obtained by performing (i) as needed. .
Step (h)
Forming a coating layer made of a polymer elastic body on at least one surface;
Step (i)
A step of relaxing in water in which the temperature is set in any temperature range of 60 to 140 ° C. and containing a surfactant.

Hereinafter, means for achieving the present invention will be described in more detail.
The sea-island fiber constituting the nonwoven fabric structure of the present invention is a multicomponent composite fiber composed of at least two types of polymers, and in the sea component polymer mainly constituting the fiber outer peripheral portion in the fiber cross section, It is a fiber having a cross-sectional shape in which different types of island component polymers are distributed. The island component polymer is normally distributed in a circular shape or a shape close to it due to the action of surface tension, but of course, depending on the ratio of the sea component polymer to the island component polymer, it may be distributed in a polygonal shape. This sea-island type fiber is extracted from the remaining island component polymer by extracting or decomposing and removing the sea component polymer at an appropriate stage after being formed into a nonwoven fabric structure and before or after impregnation with the polymer elastic body. A fiber bundle in which a plurality of fibers that are thinner than the original sea-island type fibers are converged is generated. Such a sea-island type fiber can be obtained by using a spinning method of a multicomponent composite fiber represented by a conventionally known chip blend (mixed spinning) method or a composite spinning method. The sea-island fiber is composed mainly of the outer periphery of the fiber component in the fiber cross section, compared to the split split type composite fiber such as a petal shape or a superimposed shape in which a plurality of components are alternately configured on the outer periphery of the fiber. In addition, fiber damage such as cracking, bending, and cutting during fiber entanglement, which is typically represented by needle punching, can be extremely reduced. Accordingly, a composite fiber having a finer fineness can be employed as a constituent fiber of the nonwoven fabric structure, and the degree of densification due to the entanglement can be further increased. Manufactured. The sea-island type fiber has a cross-sectional shape of the obtained ultrafine fiber that is closer to a circular shape than the peeled split type composite fiber, and the anisotropy of the fiber bundle is smaller. An ultrafine fiber bundle with high area uniformity can be obtained. In the base material for artificial leather of the present invention characterized by a non-woven structure in which a large number of fiber bundles are gathered with an unprecedented density, the sea-island fibers are used to provide a sense of fulfillment while being flexible and swell. A unique texture is also obtained.

  The polymer constituting the island component of the sea-island fiber is not particularly limited in the present invention, but polyethylene terephthalate (hereinafter referred to as PET), polytrimethylene terephthalate (hereinafter referred to as PTT), poly. Polyester resins such as butylene terephthalate (hereinafter referred to as PBT), polyester elastomers or modified products thereof; polyamides such as nylon 6, nylon 66, nylon 610, nylon 12, aromatic polyamide, semi-aromatic polyamide, polyamide elastomer Conventionally known various polymers having fiber-forming ability, such as polyolefin resins, modified resins thereof, polyolefin resins such as polypropylene, and polyurethane resins such as polyester polyurethane are suitable. Among these, polyester resins such as PET, PTT, PBT, or these modified polyesters are easily shrunk by heat treatment, and the texture and abrasion resistance, light resistance, or form stability of the processed artificial leather product with a sense of fulfillment. It is particularly preferable in view of good practical performance. In addition, polyamide-based resins such as nylon 6 and nylon 66 have hygroscopic and flexible ultrafine fibers compared to polyester-based resins, so the processed artificial leather products have a soft texture and a smooth touch. This is particularly preferred from the standpoint of practical performance such as the napped appearance and antistatic performance. These island component polymers preferably have a melting point of 160 ° C. or higher, more preferably a fiber-forming crystalline resin having a melting point of 180 to 330 ° C. When the melting point of the island component polymer is less than 160 ° C., the shape stability of the obtained ultrafine fiber cannot reach the target level of the present invention, particularly from the point of practical performance of the artificial leather product. It is not preferable. In the present invention, the melting point is measured by using a differential scanning calorimeter (hereinafter referred to as DSC) after raising the temperature from room temperature to 300 to 350 ° C. according to the polymer type at a temperature raising rate of 10 ° C./min in a nitrogen atmosphere. Then, the temperature was immediately cooled to room temperature, and the peak top temperature of the endothermic peak of the polymer observed when the temperature was immediately increased to 300 to 350 ° C. at a rate of temperature increase of 10 ° C./min was adopted. In the present invention, a colorant, an ultraviolet absorber, a heat stabilizer, a deodorant, a fungicide, an antibacterial agent, and other various stabilizers may be added to the polymer constituting the ultrafine fiber at the spinning stage.

  Since the polymer that constitutes the sea component of the sea-island fiber needs to transform the sea-island fiber into an ultrafine fiber bundle, it must be different in solubility or decomposability in the solvent or decomposing agent from the adopted island component polymer. Yes, a polymer having a low affinity with the island component polymer from the viewpoint of spinning stability, and a polymer having a melt viscosity smaller than the island component polymer under the spinning conditions or a surface tension smaller than the island component polymer It is preferable that As long as such preferable conditions are satisfied, the sea component polymer is not particularly limited in the present invention. Preferred examples include polyethylene, polypropylene, polystyrene, ethylene propylene copolymer, ethylene vinyl acetate copolymer, Examples thereof include styrene ethylene copolymers, styrene acrylic copolymers, and polyvinyl alcohol resins.

  The ratio of the sea component polymer in the sea-island fiber is preferably set at any ratio in the range of 5 to 70%, more preferably 8 to 60%, particularly preferably 12 in terms of the average area ratio in the fiber cross section. ~ 50%. When the ratio of the sea component polymer in the sea-island fiber is smaller than 5%, the spinning stability of the sea-island fiber is lowered, so that the industrial productivity is poor. Moreover, since there are few sea components removed, when the base material for artificial leather is manufactured, the space | gap which should be formed between an ultrafine fiber bundle and a polymeric elastic body is insufficient. As a result, it is not preferable because natural texture is difficult to obtain in natural leather that is soft, swelled, and has a sense of fulfillment in napped-tone artificial leather and silver-finished artificial leather. When the sea component polymer ratio exceeds 70%, the shape and distribution of the island components in the cross section of the sea-island fiber become unstable, and the quality stability is inferior. Moreover, since the load in terms of energy and cost for recovering the sea component to be removed increases and the load on the global environment also increases, such a ratio is not preferable. Furthermore, if a large amount of sea components are removed, the content of the polymer elastic body necessary to bring the shape stability of the base material for artificial leather to a desired level is remarkably increased. Such a ratio is not preferable because it is difficult to obtain the texture of artificial leather.

A composite spinning die is used for spinning the sea-island type fibers. An island component polymer flow path in which any number in the range of 6 to 150 is arranged on average for one nozzle hole, and a sea component polymer disposed so as to surround the island component polymer flow path A large number of nozzle holes having a flow path are arranged in a straight line or a circular shape at equal intervals, and are arranged in parallel in a linear shape or in a concentric shape in a circular shape. A molten sea-island type composite fiber composed of a sea component polymer and an island component polymer is continuously discharged from each nozzle hole. While substantially cooling and solidifying with cooling air at any stage from directly below the nozzle hole to the suction device described later, a high-speed air current is applied using a suction device such as an air jet nozzle, and the composite fiber is the target. It is drawn and thinned uniformly to achieve fineness. The high-speed air current is applied so that the average spinning speed corresponding to the mechanical take-up speed in normal spinning is any speed in the range of 1000 to 6000 m / min. Furthermore, while sucking from the opposite surface side of the net on the collecting surface of a conveyor belt-like mobile net, etc., while opening the composite fiber with a collision plate or airflow according to the texture of the obtained fiber web The long fiber web is formed by collecting and depositing.
When the compound spinning base is concentrically arranged, one nozzle-like suction device is generally used for one base. For this reason, a large number of sea-island fibers converge at the center point of the concentric circles during suction. In general, since a plurality of bases are arranged in a straight line to obtain a desired spinning amount, there are almost no fibers between the bundles of sea-island fibers discharged from adjacent bases. Therefore, it is important to open the fiber web in order to obtain a uniform texture. If the composite spinning bases are arranged in parallel, a linear slit-like suction device facing the base is used. For this reason, since the sea-island type fibers from between the rows arranged in parallel are concentrated at the time of suction, a fiber web having a more uniform texture can be obtained as compared with the case where the concentric bases are employed. In this respect, the parallel arrangement is more preferable than the concentric arrangement.

  It is also preferable that the obtained long fiber web is subsequently pressure-bonded while being partially heated or cooled by pressing, embossing or the like, depending on the required form stability in the subsequent process. When the melt viscosity of the sea component polymer is smaller than that of the island component polymer, the long fiber is heated or cooled at any temperature in the temperature range of about 60 to 120 ° C. without giving a high temperature up to the melting temperature. The texture of the long-fiber web can be sufficiently maintained in the subsequent steps without greatly degrading the cross-sectional shape of the sea-island fibers constituting the web. Furthermore, it is also possible to improve the shape stability of the long fiber web to a level that allows handling such as winding.

  The method of making short fibers into a fiber web by a card machine, which has been generally adopted by conventional artificial leather, is not only a card machine, but also provides an oil agent and crimp suitable for passing through the card machine, to a predetermined fiber length. A series of large-scale equipment is required for cutting, transporting and opening the raw cotton after cutting, and there are problems in terms of production speed, stable production, and cost. Another method that uses short fibers is a papermaking method. The fiber web production by this method also has the same problem because it requires equipment such as cutting and other unique equipment. In contrast to the method using these short fibers, the production method of the present invention is carried out as a single process in which the fiber web formation is not interrupted from spinning, the equipment is very compact and simple, and the production speed and cost are reduced. It ’s excellent. In addition, since it is difficult for a complex problem to occur due to a combination of various processes and facilities as in the prior art, stable productivity is also excellent. Furthermore, compared to conventional nonwoven fabric structures using short fibers, which rely only on entanglement between fibers and restraint by polymer elastic bodies, nonwoven fabric structures obtained from long fibers, and base materials for artificial leather using the same And artificial leather exhibit excellent properties in terms of physical properties such as form stability, that is, mechanical strength, surface friction durability, and adhesive peel strength on the silver surface.

According to the manufacturing method of the present invention, a nonwoven fabric structure can be stably manufactured from fibers having a very small fiber diameter, which has been difficult with a method using a conventional card machine. It is possible to obtain an extremely high-quality artificial leather that was impossible to achieve with this artificial leather. In the case of producing a nonwoven fabric structure using conventional short fibers, it is necessary to make the fiber diameter suitable for a fiber opening device or a card machine. Generally, the average cross-sectional area is 200 μm ² or more, nylon 6 and polyethylene In the case of this combination, an average fineness of about 2 dtex or more was necessary. In view of industrial stable productivity, any average cross-sectional area in the range of 300 to 600 μm ² , and in the case of a combination of nylon 6 and polyethylene, any average fineness in the range of about 3 to 6 dtex is common. Has been adopted. On the other hand, in the production method of the present invention, the fiber cross-sectional area is not substantially restricted by the equipment, the spinning stability of the fiber, the required texture of the fiber web, the required bulkiness of the nonwoven structure, Even if the production speed of the entire nonwoven fabric structure manufacturing process is within an allowable range, even very thin fibers can be used. In consideration of the spinning stability of the sea-island fiber employed by the present invention, the texture required for the fiber web, and the quality of the final artificial leather substrate and artificial leather, the average cross-sectional area is 30 μm ² or more, nylon In the case of a combination of 6 and polyethylene, the average fineness is preferably about 0.3 dtex or more. The average cross-sectional area is more preferably 50 μm ² or more, and more preferably 80 μm ² or more in view of form stability and handling in the subsequent process. In the case of a combination of nylon 6 and polyethylene, sufficiently stable industrial production is easily possible if the average fineness is in the range of about 0.8 dtex or more. By adopting the average cross-sectional area in such a range, the cross-section of the fibers substantially orthogonal to the cross-section in an arbitrary cross-section parallel to the thickness direction of the obtained fiber web is in the range of 80 to 700 pieces / mm ² . intertwining is any value, the preferably 100-600 cells / mm ^2, more preferably obtained fiber distribution present at an average number density in the range of 150 to 500 pieces / mm ^2, a subsequent process Thus, the dense nonwoven fabric structure of the present invention can be finally obtained.

In the present invention, it is necessary to improve the density of the nonwoven fabric structure of the base material for artificial leather obtained, particularly the density of the nonwoven fabric structure constituting the surface layer portion of the base material for artificial leather. For this reason, the average cross-sectional area of the ultrafine fiber bundle formed from the sea-island fibers is preferably 150 μm ² or less, and when the ultrafine fiber component is nylon 6, the average fineness of the ultrafine fiber bundle is preferably approximately 1.7 dtex or less. In order to obtain an extremely high-quality raised leather artificial leather, the average cross-sectional area is preferably 120 μm ² or less. In particular, in the case of aiming at artificial leather having a short and fine surface texture such as nubuck, the thickness is preferably 110 μm ² or less, more preferably 100 μm ² or less, and the ultrafine fiber component is nylon 6 The average fineness is more preferably about 1.2 dtex or less. The lower limit of the average cross-sectional area of the ultrafine fiber bundle does not affect the properties of the base material for artificial leather as much as the upper limit, but if it is too thin, the strength and surface friction durability of the artificial leather may decrease significantly. In order to ensure practical physical properties in the intended use of the present invention, the average cross-sectional area of the ultrafine fiber bundle needs to be at least 15 μm ² or more, preferably 30 μm ² or more, more preferably 40 μm ² or more.

By setting the average cross-sectional area of the ultrafine fiber bundle to 150 μm ² or less as described above, in the base material for artificial leather after the nonwoven fabric structure contains the polymer elastic body, any arbitrary parallel to the thickness direction thereof In terms of the cross section, an extremely dense structure that is unprecedented and has an average cross section of 1000 to 3000 fibers / mm ^{2 of} the ultrafine fiber bundle substantially orthogonal to the cross section is obtained. In the base material for artificial leather employing the conventional nonwoven fabric structure, the average cross-sectional area of the ultrafine fiber bundle itself is generally very large at about 300 to 600 μm ² , and the number density of the cross section of the ultrafine fiber bundle is 200 to 200 at the average. It was about 600 / mm ² and at most about 750 / mm ² . If it is attempted to obtain a nonwoven fabric structure having an average number density exceeding 750 pieces / mm ² in the conventional technique, the fiber bundle itself is damaged, or the cross-sectional shape of the fiber bundle is greatly deformed, and between the fiber bundles. Become very clogged. Therefore, the fiber bundle has almost no degree of freedom, and the nonwoven fabric structure is very hard. For example, only a texture like a wooden board can be obtained, and the base for artificial leather as intended in the present invention is obtained. It is completely different from the material. In addition, when a polymer elastic body is contained in a nonwoven fabric structure having an average number density of about 200 to 600 pieces / mm ² , the number density of ultrafine fiber bundles is small, although it depends on the amount to be contained. As a result, a thick polymer elastic body continuous film is formed between the adjacent bundles of ultrafine fibers. With this thick polymer elastic film, in the conventional artificial leather base material, not only the composite structure of the nonwoven fabric structure and the polymer elastic body has a hard texture, but also the region where fibers or polymer elastic bodies are solidified. In addition, only a region in which almost no fiber or polymer elastic body is present, that is, a material having extremely large uneven spots in which voids are scattered in various places, was obtained. In addition, since the ultrafine fiber bundle has a large cross-sectional area, the ultrafine fibers inside the fiber bundle are not easily subjected to the restraining action by the polymer elastic body, and therefore more polymer elastic bodies are required to give sufficient restraining action. There was a tendency to require.

  On the other hand, in the present invention, the cross-sectional area of the ultrafine fiber bundle is extremely small, and the ultrafine structure in which the number density of the ultrafine fiber bundle is extremely high, and the ground and the joint itself are mechanically controlled from the fiber web. A nonwoven structure is formed. Therefore, the thickness of the polymer elastic body for constraining the ultrafine fiber bundle can be reduced, and the cells surrounded by the polymer elastic body can be made smaller and can be distributed more uniformly. Therefore, it is possible to suppress the occurrence of remarkable coarse and dense spots such as large voids inside the base material for artificial leather. Moreover, in the conventional nonwoven fabric structure, in order to obtain a denser structure, there is no choice but to realize by appropriately combining high entanglement, high compression, high shrinkage, etc., and as a result, the apparent density, that is, the mass per unit volume is It was inevitably high. The nonwoven fabric structure of the present invention can realize an unprecedented ultra-dense structure without increasing the apparent density. Thereby, in this invention, it becomes possible to obtain a surface layer with extremely high fiber density without deteriorating the texture as a base material for artificial leather.

When the average cross-sectional area of the ultrafine fiber bundle exceeds 150 μm ² , as a method for improving the density of the surface layer of the base material for artificial leather, the average cross-sectional area of the ultrafine fiber constituting the ultrafine fiber bundle is 0.8 μm ² or less, When the ultrafine fiber component is nylon 6, a method has been proposed in which the cross-sectional shape of the ultrafine fiber bundle, and thus the surface layer of the nonwoven fabric structure, can be more easily deformed by thinning to an average fineness of approximately 0.009 dtex or less. , Actually adopted. However, since the ultrafine fibers are too thin, the shape stability of the nonwoven fabric structure is inferior, and not only can the structure be easily deformed in the length and width directions, but also easily collapsed in the thickness direction. The color developability at the time of manufacture is also insufficient, and it cannot be said to be a preferred method.

  In the present invention, the average number of ultrafine fibers constituting one ultrafine fiber bundle is 6 or more from the viewpoint of easy deformability and bendability of the fiber bundle itself, and the upper limit of the average cross-sectional area of the ultrafine fiber bundle is The number is 150 or less in view of the relationship with the lower limit of the average cross-sectional area of the ultrafine fibers and the spinning stability of the sea-island fibers. When it is desired to reduce the sea component of the sea-island fiber, the number is preferably 90 or less, more preferably 50 or less, and most preferably 10 to 40. If the average number of ultrafine fibers is 5 or less, not only the above-mentioned fiber bundles are inferior in deformability and bendability, but the ultrafine fibers are arranged on the outermost periphery of the ultrafine fiber bundles and are contained in the base material for artificial leather. The number of extra long fibers that are restrained by contact or adhesion to the polymer elastic body is increased. As a result, the restraint state of the ultrafine fiber bundle becomes excessive, and it becomes difficult to obtain a base material for artificial leather having an excellent texture as intended by the present invention. On the other hand, when the average number of ultrafine fibers exceeds 150, the restrained state by the polymer elastic body becomes excessive, contrary to the above. Although it is possible to obtain a substrate for artificial leather that is sufficiently superior when paying attention only to the texture, the conventional material has excellent physical properties such as surface friction durability represented by the pilling resistance intended by the present invention. It would be impossible to obtain a base material for artificial leather that is not present.

In the present invention, in the present invention, 80% or more of ultrafine fibers are used in consideration of the form stability of the non-woven fabric structure, the surface properties such as the pilling resistance of the base material for artificial leather or artificial leather, and the coloring property of ultrafine fibers. The cross-sectional area is 0.9 to 25 μm ² , and it is necessary that the ultrafine fiber bundle having a cross-sectional area exceeding 27 μm ² does not exist in the ultrafine fiber bundle. When the cross-sectional area of 80% or more ultrafine fibers is less than 0.9 μm ² , the object of the present invention cannot be achieved in the form stability of the nonwoven fabric structure and the color development of the napped artificial leather as described above. In addition, due to the lack of form stability of the nonwoven fabric structure, noticeable coarse and dense spots can be seen on the base material for artificial leather, and the balance of texture with the silver surface layer can be stably adjusted in the production of silver surface artificial leather. It becomes difficult to do. On the other hand, the cross-sectional area of 80% or more of ultrafine fibers exceeds 25 [mu] m ^2, and if there is microfine long fibers of more than 27 [mu] m ² in microfine fiber bundles, such as clarity and color development of napped artificial leather becomes better There is a tendency. However, because the tensile strength of the ultra-thin fibers is too strong and the fibers are difficult to cut due to resistance during surface friction, the fiber bundle is dragged out from the nonwoven fabric structure, and pilling resistance is particularly high among surface friction durability. There is a strong tendency to get worse. In order to improve the surface friction durability typified by pilling resistance, it is a general measure to increase the content ratio of the polymer elastic body in the surface layer part. Since the texture and the touch of the raised surface are cured, it is difficult to obtain a good raised artificial leather after all.

  When the obtained basis weight or thickness of the long fiber web is insufficient, wrapping is performed so that the desired basis weight and thickness are obtained (one long fiber web is supplied from a direction perpendicular to the flow direction of the process. Folding in the width direction or folding the web supplied from the direction parallel to the flow direction of the process in the length direction) and stacking (stacking multiple long fiber webs) To do. Needle punch method, etc., when the shape stability of the nonwoven fabric structure composed of sea-island fibers and the denseness of the fibers are insufficient, or when the orientation of the sea-island fibers in the thickness direction of the nonwoven fabric structure is adjusted A mechanical entanglement process is performed by a known method. As a result, the fibers constituting the long fiber web, in particular, the fibers in the adjacent layers of the layered long fiber webs that are wrapped or stacked, are three-dimensionally entangled. When entanglement processing is performed by the needle punch method, the type of needle (needle shape and count, barb shape and depth, the number and position of barbs, etc.), the number of needle punches (the number of needles implanted on the needle board) Needle punch processing density per unit area multiplied by the density and the number of strokes that cause the board to act per unit area of the long fiber web), needle punch depth (depth at which the needle acts on the long fiber web) Various processing conditions such as these are selected as appropriate.

  As for the type of needle, those similar to those used in the production of artificial leather using conventional short fibers can be used as appropriate, but in order to obtain the effects of the present invention, the needle count, the depth of the barb, The number of barbs is particularly important, and it is preferable to use mainly the types of needles described below.

  The needle count is a factor that affects the density and surface quality obtained after processing, and at least the size of the blade portion (the portion where the barb at the tip of the needle is formed) is No. 30 (the cross-sectional shape is an equilateral triangle) If it is circular, the diameter needs to be smaller (thin) if it is circular, and the diameter is preferably about 0.73 to 0.75 mm, preferably 32 (about 0.68 to 0.70 mm) to 46 (0). .33 to 0.35 mm), and more preferably in the range of 36 (height 0.58 to 0.60 mm) to 43 (height 0.38 to 0.40 mm). A needle with a blade size larger than 30 (thick) has a high degree of freedom in the shape and depth of the barb and is preferable in terms of the strength and durability of the needle. Therefore, it is difficult to obtain a dense fiber assembly state and surface quality intended by the present invention. Moreover, since the frictional resistance between the fibers in the long fiber web and the needle becomes too large, it is not preferable because it is necessary to apply an excessive amount of oil for needle punching. On the other hand, a needle having a blade size smaller than No. 46 is not only suitable for industrial production in terms of strength and durability, but also makes it difficult to set a barb having a suitable depth in the present invention. The cross-sectional shape of the blade portion is preferably an equilateral triangle in the present invention from the viewpoint of easy catching of the fiber and small frictional resistance.

  The barb depth in the present invention is the height from the deepest part of the barb to the barb tip. In general-shaped barbs, the height to the tip of the barb protruding outward from the side of the needle (sometimes referred to as kick-up) and the depth to the deepest part of the barb formed inside the needle side (throat depth) It also refers to the combined height. The barb depth needs to be at least the diameter of the sea-island fiber, and is preferably 120 μm or less. If the barb depth is less than the diameter of the sea-island fiber, it is not preferable because the sea-island fiber becomes very difficult to be caught by the barb. On the other hand, when the barb depth exceeds 120 μm, the fibers are very easily caught, but a needle punch mark having a large hole diameter tends to remain on the surface of the nonwoven fabric structure, and the dense fiber aggregation state and surface quality intended by the present invention are obtained. It becomes difficult. The barb depth is preferably any multiple in the range of 1.7 to 10.2 times the diameter of the sea-island fiber, more preferably selected from the range of 2.0 to 7.0 times. Is a multiple of If the barb depth is less than 1.7 times, the sea-island fiber is not easily caught by the barb, so even if the number of punches described later is increased, the entanglement effect commensurate with it may not be obtained. On the other hand, even if it exceeds 10.2 times, rather than improving the ease of catching sea-island fibers, the tendency to increase damages such as cutting and cracking of sea-island fibers is increased, which is not preferable.

  The number of barbs in the present invention may be appropriately selected so as to obtain a desired entanglement effect in a range of 1 to 9, but at least the number of needles mainly used for needle punch entanglement processing, that is, the number of punches described later. A needle used for punching of 50% or more preferably has a barb number in the range of 1 to 6 in order to obtain a non-woven structure having a dense structure. Further, in the present invention, the number of needle barbs used for the needle punch entanglement process does not have to be one, for example, one and nine, one and six, three and nine different barbs, etc. Any number of needles may be combined as appropriate and used in any order. In needles having a plurality of barbs, the positions of the respective barbs include those having different distances from the needle tip side and those having several barbs at the same distance. Examples of the latter needle include a needle having a regular triangular cross-sectional shape and one barb at each of the three apex angles at the same distance from the tip. In the present invention, the former needle is mainly used as the needle used for the entanglement treatment. This is because a needle having a plurality of barbs at the same distance has an effect that the blade portion of the needle is apparently thick and the depth of the barb is large, so that the entanglement effect is high, while the blade portion is This is because the inconvenience seen when the barb is too thick and the barb is too deep appears. Furthermore, when the needle punching process is performed using the latter needle, a large number of fibers of ten to several tens are bundled in one place and oriented in the thickness direction of the nonwoven fabric structure. There is also a tendency that a dense structure as intended by the present invention becomes difficult to obtain as the value increases. That is, in an arbitrary cross section parallel to the thickness direction of the nonwoven fabric structure, there are many fibers substantially parallel to the cross section, but the number density of fibers substantially orthogonal to the cross section tends to extremely decrease. However, since a strong entanglement effect can be obtained even with a small number of punches, it is also preferable to use the latter needle as part of the entanglement process. For example, in an arbitrary stage from the initial stage to the middle stage of the entanglement process, the entanglement process is performed with the latter needle to the extent that the target dense structure is not hindered, and then the former needle is used to obtain the target dense structure. Also good.

The total number of punches of the needle is preferably any value in the range of 300 to 4000 punch / cm ² , more preferably in the range of 500 to 3500 punch / cm ² . In the case of using a needle having several barbs at the same distance as described above, it is about 300 punch / cm ² or less, preferably about 10 to 250 punch / cm ² . When the needle punching process exceeding 300 punch / cm ² is performed, the fibers are oriented in the thickness direction. Therefore, even if the needle punching process, the shrinking process, and the pressing process are performed thereafter, the number of the nonwoven fabric structures is increased. It tends to be difficult to increase the density.

The average number density (number per unit area of the cross section of the fiber substantially perpendicular to the cross section in an arbitrary cross section parallel to the thickness direction) necessary for the nonwoven fabric structure composed of sea-island fibers is 600 to 4000 / mm ^2. , Preferably 700 to 3800 pieces / mm ² , more preferably any value in the range of 800 to 3500 pieces / mm ² . In order to obtain a dense structure having such an average number density range, it is preferable to use not only the entanglement process such as the needle punch process but also the heat shrink process using hot air, hot water, steam, etc. By combining one or more of these processes, finally, a dense structure intended by the present invention can be obtained. Of course, in addition to the entanglement process and the shrinking process, it is also preferable to perform the press process simultaneously with or before or after the process.

After entanglement treatment by needle punch, after entanglement treatment by needle punch and heat shrinkage treatment, or after heat shrinkage treatment, 50% or more of the density (average number density) required for the nonwoven fabric structure composed of the sea-island fibers described above It is preferable to make it 55 to 130%. For example, if the final target is 2000 / mm ² , the average number density is preferably at least 1000 / mm ² or more.

In order to obtain an extremely dense nonwoven fabric structure by the densification treatment mainly using the needle punch process using the preferred needle, the total number of punches is preferably in the range of 800 to 4000 punches / cm ² , More preferably, it is the range of 1000-3500 punch / cm < ² >. When the number of needle punches is less than 800 punches / cm ² , not only is densification insufficient, but in particular, there is a strong tendency that the nonwoven fabric structure is not sufficiently integrated due to entanglement of fibers between different layers of the long fiber web. On the other hand, when it exceeds 4000 punches / cm ² , although it depends on the shape of the above-mentioned needle, damage such as cutting or cracking by the fiber needle is conspicuous, and when the fiber damage is particularly severe, While the form stability is greatly lowered, the density may be lowered.

  From the viewpoint of the mechanical properties such as form stability and tear strength of the nonwoven fabric structure and artificial leather substrate obtained, and the orientation of the fibers in the thickness direction, It is preferable that the barb acts more. Therefore, the punch depth of the needle is preferably set to such a depth that at least the barb on the most distal side of the needle penetrates the entire thickness of the long fiber web. Also, in order to realize an unprecedented dense structure, punching of 50% or more of the number of punches must be set to a depth at which the barb penetrates the long fiber web, and punching of 70% or more is required. It is preferred that the barbs are deep enough to penetrate the long fiber web. However, if the punch depth is too large, fiber damage due to barbs tends to be noticeable, and punching marks tend to remain on the surface of the nonwoven fabric structure. It is necessary to pay attention to these points.

  When adopting the needle punch method for the entanglement process, in order to suppress damage to the fiber due to the needle, and to suppress charging and heat generation caused by strong friction between the needle and the fiber, after the long fiber web manufacturing process, It is preferable to apply the oil agent at any stage before the entanglement treatment step. As a method for imparting, a known coating method such as a spray coating method, a reverse coating method, a kiss roll coating method, a lip coating method, etc. can be adopted, and among them, the spray coating method is non-contact with the long fiber web, And since the low-viscosity oil agent which permeates the long fiber web inner layer in a short time can be used, it is most preferable. The term “long fiber web manufacturing process and later” as used herein refers to the period after the stage where sea-island fibers are melt-spun and collected and deposited on a collection surface such as a mobile net. In the present invention, the oil agent to be applied before the entanglement treatment may be an oil agent composed of one type of component, but preferably, a plurality of types of oil agents having different effects are used, and these are mixed and applied or sequentially applied. preferable. The oil agent used in the present invention is an oil agent having a high sliding effect that reduces friction between the needle and the fiber, that is, friction between the metal and the polymer. Specifically, a polysiloxane-based oil agent is preferable, and dimethylsiloxane is mainly used. The oil agent is more preferable. As an oil agent used in combination with this oil agent having a high sliding effect, the slipping effect is too strong, and the entanglement effect due to catching on the barb is locally reduced remarkably, especially the friction coefficient between fibers is remarkable. It is preferable to use an oil agent with a high frictional effect that can prevent the maintenance of the entangled state from being reduced to a low level. Specifically, a mineral oil-based oil agent is preferable. In addition, when charging due to friction is significant, it is also preferable to use a surfactant, for example, a polyoxyalkylene surfactant as an antistatic agent.

The long fiber web, its stack, or the long fiber web after the entanglement treatment is subjected to heat shrink treatment so as to have a desired density in warm water, high temperature atmosphere, or high temperature and high humidity atmosphere as necessary. . For example, when obtaining the density of a nonwoven fabric structure having an average number density of about 800 to 1000 pieces / mm ^{2, the} target density is first made to be about 500 to 700 pieces / mm ² by entanglement treatment. Shrink processing to become. For the heat shrink treatment, the long fiber web is formed of a shrinkable sea-island fiber, or a long-fiber web is produced by using a shrinkable fiber in addition to the sea-island fiber, Preferably, the webs are manufactured separately and stacked. In order to obtain a shrinkable sea-island type fiber, a heat-shrinkable polymer may be employed and spun for either or both of the sea component polymer and the island component polymer. Examples of the heat-shrinkable island component polymer include polyamide resins such as polyester resins and copolymers of different nylons, and polyurethane resins. The shrinkage treatment condition is not particularly limited as long as it is a temperature at which sufficient shrinkage can be obtained, and may be appropriately set according to the shrinkage treatment method to be employed, the processing amount of the processing object, and the like. For example, when shrinkage treatment is performed by introducing into warm water, the shrinkage treatment is preferably performed at any temperature within a temperature range of 70 to 150 ° C.

In addition to the above-described entanglement treatment by needle punching and heat shrinkage treatment, it is necessary prior to the impregnation treatment of the polymer elastic body to be described later in order to make the nonwoven fabric structure made of sea-island fibers a desired density. Accordingly, it is also preferable to employ a press process. For example, when aiming at a density with an average number density of about 800 to 1000 / mm ² , the target density is first increased to about 600 to 800 / mm ² by entanglement treatment. Press processing may be performed. In the case of adopting the press treatment, it is preferable to use the heat treatment in combination with the heat shrink treatment and immediately press the heat treatment while the heat is applied. By adopting such a processing method, the densification by the pressing process proceeds almost simultaneously with the shrinking process, so it is possible to obtain a uniform densified state rather than simply performing the pressing process. It is also possible to obtain excellent production efficiency. In the sea-island type fiber constituting the nonwoven fabric structure, when the softening temperature of the sea component polymer is 20 ° C. or more, preferably 30 ° C. or more lower than the softening temperature of the island component polymer, the press treatment used in combination with the heat shrink treatment is performed by densification. It is valid. In this case, by heating to a temperature range from a temperature close to the softening temperature of the sea component polymer to a temperature lower than the softening temperature of the island component polymer, only the sea component polymer in the sea-island fiber is softened or close to that state. When pressed in this state, the nonwoven fabric structure is compressed into a denser state, and if this is cooled to room temperature, a nonwoven fabric structure fixed in a desired dense state can be obtained. Advantages other than the densification of the press treatment include an effect that the surface of the nonwoven fabric structure can be fixed in a more smooth state. By smoothing, it is possible to more effectively obtain a very dense aggregate state of the ultrafine fiber bundles, which is the greatest feature of the base material for artificial leather of the present invention. That is, since the surface of the base material for artificial leather can be made smoother, it becomes possible to reduce the amount of grinding in the napping formation processing such as buffing in the production of napped-tone artificial leather. In the production of the artificial leather, it is possible to stably form an extremely thin silver surface layer having a smooth surface and a thickness of 50 μm or less without subjecting the surface of the substrate to hot pressing or buffing.

A dense nonwoven fabric structure having an average number density in the range of 600 to 4000 / mm ² thus obtained preferably contains a predetermined amount of the elastic polymer before removing the sea component polymer. . Examples of the method of inclusion include a method in which a solution or dispersion of a polymer elastic body is impregnated and solidified by a conventionally known dry method or wet method. As the impregnation method, after immersing the nonwoven fabric structure in a bath filled with a polymer elastic body fluid, a process of squeezing to a predetermined liquid content state with a press roll or the like is performed once or a plurality of times. Any of various conventionally known coating methods such as a nip method, a bar coating method, a knife coating method, a roll coating method, a comma coating method, and a spray coating method can be employed. One type of method or a plurality of types of methods may be combined.

  Any polymer elastic body to be contained in the nonwoven fabric structure can be used as long as it is conventionally used for a base material for artificial leather. Specific examples include at least one polymer polyol having an average molecular weight of 500 to 3000 selected from polyester diol, polyether diol, polyether ester diol, polycarbonate diol, and the like, 4,4′-diphenylmethane diisocyanate, isophorone diisocyanate, hexa Combined with at least one polyisocyanate selected from aromatic, alicyclic, and aliphatic diisocyanates such as methylene diisocyanate as a main component, and two or more active hydrogens such as ethylene glycol and ethylenediamine Examples thereof include various polyurethanes obtained by combining at least one kind of low-molecular compound having atoms in a predetermined molar ratio and reacting them in one step or multiple steps. The base material for artificial leather obtained by adopting polyurethane as the main polymer elastic body is excellent in balance of texture and mechanical properties, and also in balance including durability. preferable. As the polymer elastic body, different types of polyurethane may be mixed and contained, or different types of polyurethane may be contained in a plurality of times. In addition to polyurethane, synthetic rubber, polyester elastomer, You may make it contain as a polymeric elastic body composition which added polymeric elastic bodies, such as acrylic resin, as needed.

  A non-woven fabric structure is impregnated with a polymer elastic body fluid such as a solution or dispersion of a polymer elastic body, and then the polymer elastic body is solidified by a conventionally known dry method or wet method. Fix in the body. The dry method here refers to all methods for fixing a polymer elastic body in a nonwoven fabric structure by removing a solvent or a dispersant by drying or the like. In addition, the wet method here refers to a non-woven structure impregnated with a polymer elastic body fluid treated with a non-solvent or coagulant of the polymer elastic body, or a polymer elastic body fluid to which a heat-sensitive gelling agent is added. The general method of temporarily fixing or completely fixing the polymer elastic body in the nonwoven fabric structure prior to the removal of the solvent or the dispersant by heat-treating the impregnated nonwoven fabric structure or the like.

  In the polymer elastic body fluid, various additives blended in the polymer elastic body fluid contained in the conventional artificial leather base material such as a colorant, a coagulation regulator, and an antioxidant may be appropriately blended. The amount of the polymer elastic body or polymer elastic body composition to be contained in the nonwoven fabric structure may be adjusted as appropriate according to the mechanical properties, durability, texture, etc. required for the intended use. When the basis weight of the nonwoven fabric structure composed of fiber bundles is 100, the basis weight of the polymer elastic body is preferably 10 to 150% by mass, and more preferably 30 to 120% by mass. When the content of the polymer elastic body is less than 10% by mass, the polymer elastic body is interposed between adjacent ultrafine fiber bundles inside the base material for artificial leather, The effect of suppressing the movement of the ultrafine fiber bundle in the length direction becomes insufficient by bonding. In particular, in the case of napped-toned artificial leather, it is difficult to obtain the effects of the present invention in terms of surface friction durability such as pilling resistance. On the other hand, when the content of the polymer elastic body exceeds 150% by mass, there is no problem such as the above-mentioned adverse effect on the pilling resistance, but rather the surface friction durability tends to be improved. On the other hand, the base material for artificial leather, or the texture when it is made into silver artificial leather or napped artificial leather, the texture becomes noticeably hardened and the rubber feel becomes stronger. Is not preferable because it tends to be rough.

  As a measure for suppressing the degree of texture hardening due to the inclusion of the polymer elastic body, the conventional artificial leather manufacturing method can dissolve and remove polyvinyl alcohol resin and the like before impregnating and solidifying the polymer elastic body fluid. The resin is applied according to the amount of the polymer elastic body applied to the nonwoven fabric structure. When the polymer elastic body is applied, since the polyvinyl alcohol resin is interposed between the fiber constituting the nonwoven fabric structure and the polymer elastic body, the fiber and the polymer elastic body are in contact with each other after removing the resin. Or it becomes difficult to adhere. However, in the present invention, a non-woven fabric structure in which fibers are densely gathered, which is unprecedented, is employed, and thin sea-island fibers or ultrafine fiber bundles that are not found in conventional methods for manufacturing artificial leather substrates are used. Even if a polyvinyl alcohol resin or the like is simply applied, the fibers constituting the nonwoven fabric structure are uniformly coated with the resin, and the voids for containing the polymer elastic body between the coated fibers are uniformly formed. It is difficult to exist. Further, since the region where the resin is locally hardened in the nonwoven fabric structure and the region where the resin hardly exists are scattered in various places, it is not a method that can be preferably employed in the present invention in order to avoid hardening of the texture. . However, for example, for the purpose of temporarily fixing between the fibers of the nonwoven fabric structure to improve the shape stability and supplementarily improving the process passability of the polymer elastic body application process, etc. As long as it is not hindered, the resin may be applied in a small amount of about 20% or less by mass ratio to the basis weight of the nonwoven fabric structure.

As a method for removing the sea component polymer from the sea-island type fibers constituting the nonwoven fabric structure before or after the inclusion of the polymer elastic body, a non-solvent or non-decomposing agent for the island component polymer is used. A method of treating a nonwoven fabric structure with a liquid that is also a non-solvent or non-decomposing agent for a macromolecular elastic body and a liquid that is a solvent or decomposing agent for a sea component polymer when the body is removed after being incorporated Is preferably employed in the present invention. When the island component polymer is a polyamide resin or polyester resin suitable for the present invention, specific examples of the liquid suitably used for the sea component polymer removal treatment include toluene, trichloroethylene if the sea component polymer is polyethylene. Organic solvents such as tetrachloroethylene can be used. If the sea component polymer is a polyvinyl alcohol resin that is soluble in warm water, warm water at a soluble temperature can be used, and the sea component polymer can be easily alkali-degradable modified. If it is polyester, alkaline decomposition agents, such as sodium hydroxide aqueous solution, are mentioned. Even when the elastic structure is not contained in the nonwoven structure at the sea component polymer removal treatment stage, even when the polyurethane which is a preferred example in the present invention is contained, the solvent or the decomposition agent Any of the liquids described above can be used. In particular, when an organic solvent or an alkaline decomposing agent is employed, it is preferable to appropriately control the composition of the polymer elastic body to be contained to suppress deterioration of the polymer elastic body due to the removal treatment. By such sea component polymer removal treatment, the sea-island type fibers are transformed into ultrafine fiber bundles composed of island component polymers, and the base material for artificial leather of the present invention having a basis weight of preferably 60 to 1800 g / m ² is obtained.

  The base material for artificial leather obtained in this way is adjusted in thickness by slicing into multiple sheets in the thickness direction and grinding the back surface as necessary, as in conventional artificial leather manufacturing. Or the surface to be the back surface or the surface to be the front surface is treated with a liquid containing a polymer elastic body or a solvent for the ultrafine fiber bundle. Thereafter, at least the surface to be surfaced is raised by a method such as buffing to form a fiber raised surface mainly composed of ultrafine fibers, thereby obtaining a napped artificial leather such as suede or nubuck. Moreover, a silver-tone artificial leather can be obtained by forming a coating layer made of a polymer elastic body on the surface to be the surface.

  For the formation of the fiber raised surface, any known method such as buffing with sandpaper or knitted cloth or brushing can be used. In addition, before or after the raising treatment, a treatment that can dissolve or swell the polymer elastic body or the ultrafine fiber bundle, for example, treatment containing dimethylformamide (DMF) or the like if the polymer elastic body is polyurethane. If the liquid or the ultrafine fiber bundle is a polyamide resin, a treatment liquid containing a phenol compound such as resorcin may be applied to the surface to be raised. Thereby, it is possible to finely adjust the restraint state of the ultrafine fiber bundle by adhesion of the polymer elastic body or the ultrafine fiber bundle, the ultrafine fiber napping length of the napped-tone artificial leather, the surface friction durability, and the like.

  For the formation of a coating layer made of a polymer elastic body, a liquid containing the polymer elastic body is directly applied to the surface of the artificial leather base material, or once the liquid is applied onto a support base material such as a release paper. Any known method such as a method of bonding to a base material for artificial leather can be used. The polymer elastic body used for the coating layer to be formed is the same as the polymer elastic body for inclusion in the non-woven fabric structure described above, and is known as a polymer elasticity known as a coating layer for conventional silver-tone artificial leather Any body can be used. If the thickness of the coating layer to be formed is about 300 μm or less, there is no particular limitation because it is possible to produce a silver-tone artificial leather having a well balanced texture with the artificial leather substrate of the present invention. In the case of producing a silver-tone artificial leather having an extremely smooth and uniform surface layer obtained by a dense assembly state of ultrafine fiber bundles which is the greatest feature of the base material for artificial leather of the present invention, the thickness is 100 μm. It is better to form a coating layer in the range of about the following, preferably about 80 μm or less, more preferably about 3 to 50 μm. By forming the coating layer with such a thickness, an extremely fine natural leather-like crease and wrinkle can be formed. It is also possible to obtain a silver-tone artificial leather.

  Such napped-tone artificial leather or silver-tone artificial leather may be dyed at any stage after the sea-island type fibers are transformed into ultrafine fiber bundles. In the present invention, an acid dye, a metal complex dye, a disperse dye, a sulfur dye, a sulfur vat dye, or the like, which is appropriately selected depending on the type of fiber, padder, jigger, circular, Wins, etc. Any conventional dyeing method using a known dyeing machine usually used for dyeing artificial leather can be employed. In addition to dyeing, if necessary, mechanical padding treatment in a dry state, relaxation treatment in a wet state using a dyeing machine or a washing machine, softening agent treatment, flame retardant, antibacterial agent, deodorant Resins other than those mentioned above, such as water and oil repellents, functional treatments such as silicone resins and silk protein-containing treatments, grip modifiers such as gripping resins, colorants and enamel coating resins It is also preferable to perform a finishing process such as a design imparting process to be applied. Since the base material for artificial leather of the present invention has a structure in which very fine fiber bundles are gathered very densely, relaxing treatment and softening agent treatment in a wet state remarkably improve the texture. This treatment is preferably employed in artificial leather. For example, if it is a relaxation treatment, it can be treated in water that contains a surfactant in the temperature range of about 60 to 140 ° C., so that it has a flexible and bulging feeling that is not inferior to natural leather, but has a dense structure itself. It is also possible to obtain an artificial leather whose feeling is not impaired.

  Next, embodiments of the present invention will be described with specific examples, but the present invention is not limited to these examples. In the examples, “part” and “%” relate to mass unless otherwise specified.

(1) Cross-sectional area of ultrafine fibers, average cross-sectional area of ultrafine fiber bundles, and average number of focusing in ultrafine fiber bundles Scanning electron microscope (about 100 to 300 times) any cross section parallel to the thickness direction of the base material for artificial leather ). Twenty ultrafine fiber bundles oriented almost perpendicularly to the cross section from the observation field were selected uniformly and randomly. Subsequently, the cross section of each selected ultrafine fiber bundle was enlarged to a magnification of about 1000 to 3000 times, and the cross-sectional area of the ultrafine fiber and the number of bundles in the ultrafine fiber bundle were obtained.
Further, for the selected 20 ultrafine fiber bundles, the cross sectional area of the ultra fine fiber bundles was determined by calculation from the cross sectional area of the ultra fine fibers measured by the above method and the number of bundles. The maximum cross-sectional area and the minimum cross-sectional area were deleted, and the remaining 18 cross-sectional areas were arithmetically averaged to determine the average cross-sectional area of the ultrafine fiber bundles constituting the base material for artificial leather. In addition, when the number of ultrafine fibers is not constant and distributed, the base material for artificial leather can be obtained by arithmetically averaging the number of bundles of 18 ultrafine fiber bundles excluding the maximum and minimum. The average number of bundles of ultrafine fiber bundles to be formed was determined.

(2) Average number density (number of cross sections of ultrafine fiber bundles present per unit area of a cross section parallel to the thickness direction)
An arbitrary cross section parallel to the thickness direction of the base material for artificial leather was observed with a scanning electron microscope (about 100 to 300 times). The number of cross-sections determined to be approximately perpendicular to the length direction of the ultrafine fiber bundle in each observation field is observed so that the total observation area is 0.5 mm ² or more. I counted. By dividing the total number by the total observation area, the number of microfiber bundle cross sections existing per 1 mm ² was obtained. The average number density of the base material for artificial leather was obtained by arithmetically averaging the number of cross sections of the ultrafine fiber bundle per 1 mm ² in the entire observation visual field.

(3) Appearance evaluation of napped-toned artificial leather Five panelists selected by those skilled in the art of artificial leather evaluated the appearance of napped-toned artificial leather visually according to the following criteria, and the most panelists gave it. Evaluation was made into the appearance evaluation result.
A: The density of the napped surface is extremely high as a whole, and it is smooth without any roughness when touched with a hand.
B: The density of the napped surface is slightly rough as a whole, or is relatively high as a whole, but the density is clearly low and the rough parts are scattered. is there.
C: It is a rough raised surface as a whole, and there is considerable roughness when touched by hand.

(4) Evaluation of texture of napped-toned artificial leather When the thickness of the obtained napped-toned artificial leather is less than 0.8 mm, it is sewed on a golf glove, and when the thickness is 0.8 to 1.2 mm It was sewn on the jacket, and when the thickness exceeded 1.2 mm, it was sewn on the sofa. The five panelists selected from those skilled in the art of artificial leather wear the texture of the napped artificial leather according to the following criteria, and the evaluation given by the most panelists was used as the texture evaluation result.
A: A texture that is flexible and swells, but also has a sufficient sense of fullness, and the sewn product has a good fit.
B: The texture is somewhat unsatisfactory due to lack of flexibility, swelling, and fulfillment, and the fit of the sewn product is inadequate. The same).
C: Any of softness, swelling, and fulfillment is significantly inferior, or the texture is inferior, and the fit of the sewn product is poor (in terms of texture and fit, It is inferior to general napped artificial leather).

(5) Evaluation of surface abrasion durability of napped-tone artificial leather Surface of napped-toned artificial leather obtained under the conditions of a load of 12 kPa and a wear frequency of 50000 in accordance with the Martindale abrasion test measurement method specified in JIS L1096 Abraded. When the mass difference before and after the treatment (wear loss) was 50 mg or less, it was determined that the wear resistance was good. Moreover, the pilling generation | occurrence | production state (increase / decrease) of the napped-tone artificial leather surface before and behind a process was compared visually by the following references | standards. Those having good wear resistance and a pilling occurrence state of A or B were evaluated as having excellent surface wear durability.
A: No increase in pilling is observed (decrease in pilling due to cutting of napped hair may be observed)
B: Although a slight increase in pilling is seen, there is almost no increase in pilling that can be felt by touching with the hand. C: Pilling is clearly increased and pilling that can be felt by touching by hand. Obviously increased

(6) Appearance evaluation of silver-tone artificial leather Five panelists selected by those skilled in the art of artificial leather field evaluated the appearance of silver-tone artificial leather according to the following criteria, and the most panelists gave it. Evaluation was made into the appearance evaluation result.
A: The smoothness of the surface is extremely high, the creases are fine, and it is a natural leather tone.
B: Locations where the smoothness of the surface is clearly inferior are scattered, or the overall smoothness is slightly inferior, and even in the creases, rough portions are scattered, or the entire surface is slightly rough .
C: The smoothness of the surface is clearly inferior, and the wrinkles are generally rough.

(7) Evaluation of the texture of the artificial silver-tone leather When the thickness of the obtained artificial leather is less than 0.8 mm, it is sewed on a golf glove and the thickness is 0.8-1.2 mm Was sewn on the jacket, and when the thickness exceeded 1.2 mm, it was sewn on the sofa. The five panelists selected from those skilled in the art of artificial leather wear the texture of the silver-tone artificial leather according to the following criteria, and the evaluation given by the most panelists was used as the texture evaluation result.
A: Although it is flexible and swells, it has a satisfactory feeling of fullness and a feeling of unity between the silver surface layer and the base material, and has a good fit as a sewn product.
B: The texture is slightly unsatisfactory due to lack of flexibility, swelling, fullness, or unity, and the fit as a sewn product is insufficient (the conventional general silver in texture and fit) It is the same level as surface-artificial leather).
C: Any of softness, swelling, fullness, and unity is significantly inferior, or all of them are inferior in texture, and the fit as a sewn product is poor (texture and fit) Inferior to conventional conventional silver-tone artificial leather).

(8) Evaluation of adhesion peel strength of silver surface-like artificial leather 250 mm in the length direction and 25 mm in the width direction were cut out from any part of the obtained silver-tone artificial leather, and three test pieces in the length direction were obtained. Obtained. Similarly, 25 mm in the length direction and 250 mm in the width direction were cut out to obtain three test pieces in the width direction. The surface of each test piece was wiped with gauze soaked with methyl ethyl ketone (MEK) to remove the dirt, and then dried at room temperature for about 2 to 3 minutes while preventing the dirt from adhering. After lightly buffing one side of the crepe rubber sheet cut out to a length of 150 mm, a width of 27 mm, and a thickness of 5 mm, dirt on the buffed surface was removed with MEK in the same manner as the test piece and dried. 5% of a curing agent was added to a commercially available polyurethane adhesive for shoes (solid content concentration 20%) and mixed well, and 0. 0 mm of the mixture was placed in an area of about 90 mm from one end in the longitudinal direction of each of the test piece and the rubber sheet. 1-0.2 g was immediately applied to a uniform thickness. The test piece after application and the rubber sheet were dried for 2 to 3 minutes at room temperature, and further heated for about 3 minutes in a dryer at 100 to 120 ° C. to initiate a curing reaction. Next, the test piece and the adhesive-coated surface of the rubber sheet were stuck together and uniformly bonded, and finally the curing reaction was promoted by heating in a dryer at 60 to 80 ° C. for about 1 hour to sufficiently adhere the measurement. I got a piece.

  Fold the unbonded part of the test piece so that the unbonded part of the test piece and the unbonded part of the rubber sheet are at an angle of approximately 180 °, and then the upper and lower chucks of the tensile tester with the rubber sheet facing down (Chuck distance: 150 mm). A 180 ° peel test was performed at a pulling rate of 100 mm / min, and the stress value during peeling was recorded on a chart. If the test piece is too hard to be 180 ° peeled off and close to a T-shaped peel, a metal reinforcing plate with a length of about 150 mm, a width of 30 mm, and a thickness of about 2 mm is used as a rubber sheet for the measurement piece. You may make it hold | grip to a chuck | zipper with it piled up on the back surface side, and it may be made not to be in the state of T-shaped peeling. Exclude the maximum value at the start of peeling and the minimum value immediately after it from the stress value recorded on the chart, and use the average stress value visually judged from the stress curve of the other part as the adhesion peel strength value of the test piece It was. The strength values obtained for each of the three test pieces in the length direction and the width direction were arithmetically averaged to obtain an evaluation result of the adhesive peel strength in each of the length direction and the width direction.

Example 1
Low density polyethylene (LDPE) as the sea component polymer and nylon 6 (Ny6) as the island component polymer were individually melted. In the spinneret for composite spinning in which a large number of nozzle holes are arranged in parallel, which can form a cross section in which 25 island component polymers having a uniform cross-sectional area are distributed in the sea component polymer, the molten polymer is combined with the sea component polymer in the cross section. It was supplied in a pressure balance such that the average area ratio of the island component polymer was sea / island = 50/50, and was discharged from the nozzle hole at a die temperature of 290 ° C. The sea-strip type fiber with an average cross-sectional area of 160 μm ² (about 1.6 dtex) was spun by an air jet / nozzle type suction device with the air pressure adjusted so that the average spinning speed was 3600 m / min. This was continuously collected on the net while being sucked from the back side. Adjust the net moving speed to adjust the amount of deposit, and lightly hold it with an embossing roll kept at 80 ° C, the average basis weight is 30 g / m ² , and the cross section of the sea-island fiber is average on the cross section parallel to the thickness direction A long fiber web having 350 pieces / mm ² and having a form stabilized to such an extent that winding was possible was obtained.

The above-mentioned long fiber web was formed into a layered long fiber web having an average of 20 layers using a cross wrapper apparatus. The surface of the layered long fiber web was sprayed with an oil agent mainly composed of a dimethylpolysiloxane-based slipping oil agent and mixed with a mineral oil-based oil agent and an antistatic agent, and then entangled by a needle punch method. Needle punch is needle No. 40, barb depth of 40 μm, needle A with a single barb and an equilateral triangular section A, and needle count No. 42, barb depth of 40 μm, with six barbs and an equilateral triangular section of needle B Used as an auxiliary, with a punch depth at which three barbs from the tip of needle A and needle B all penetrate in the thickness direction, with a total number of punches of 1200 punch / cm ² from both sides The sea-island fibers were entangled in the thickness direction. Next, after heat-shrinking at an atmospheric temperature of 150 ° C., pressing is performed with a metal roll kept at 10 ° C., so that the cross-section of the sea-island fiber is on the cross-section parallel to the thickness direction with an average basis weight of 650 g / m ^2. A nonwoven fabric structure in which sea-island type fibers with an average of 1200 pieces / mm ² were gathered very densely was obtained.

The resulting nonwoven fabric structure was impregnated with a polymer elastic body fluid consisting of 13 parts of a polyurethane composition mainly composed of polyether polyurethane and 87 parts of dimethylformamide (hereinafter referred to as DMF), and wet coagulated in water. After removing DMF by washing with water, the low-density polyethylene in the sea-island fiber is extracted and removed with heated toluene, then toluene is removed azeotropically in a hot water bath, and dried, so that nylon 6 extra-fine fibers A base material for artificial leather according to the present invention having a thickness of about 1.3 mm in which polyurethane was contained inside a non-woven fabric structure composed of bundles of ultrafine fibers.
The average cross-sectional area of the ultrafine fibers measured by the above method was 2.6 μm ² , the number of focusing was 25, and the ultrafine fibers having a substantially uniform cross-sectional area were converging. The average cross-sectional area of the ultrafine fiber bundle was 68 μm ² , and no ultrafine fiber having a cross-sectional area exceeding 27 μm ² was present in the ultrafine fiber bundle. The number of cross sections of the ultrafine fiber bundles existing per unit area of the cross section parallel to the thickness direction is 1700 / mm ^{2 on} average, and most of the ultrafine fiber bundles are not bonded to the polymer elastic body. .

Example 2
The base material for artificial leather obtained in Example 1 was divided into two in the thickness direction by slicing. After buffing the divided surface with sandpaper and adjusting the thickness to an average thickness of 0.62 mm, the other surface is buffed with an emery buff machine with sandpaper set to raise and trim the surface of the ultrafine fiber raised surface. Formed. Furthermore, using Irgalan Red 2GL (Ciba Specialty Chemicals), it dye | stained by the density | concentration of 4% owf, Then, it brushed and finished the hair and obtained nubuck-like artificial leather. The number of ultrafine fiber bundle cross-sections existing per unit area of the cross section parallel to the thickness direction measured by the above method is 1500 / mm ² , while having a highly raised napped surface, Had no color development. The appearance, texture, and surface wear durability were all very good, and it was a napped artificial leather having the intended effect of the present invention. The evaluation results are shown in Table 1.

Example 3
In Example 1, the polymer elastic body liquid impregnated into the nonwoven fabric structure was replaced with a liquid composed of 18 parts of a polyurethane composition mainly composed of a mixed polyurethane composed of 65% polycarbonate polyurethane and 35% polyether polyurethane and 82 parts DMF. In the same manner, a base material for artificial leather of the present invention having a thickness of about 1.0 mm in which polyurethane was contained inside a non-woven fabric structure made of ultrafine fiber bundles in which ultrafine fibers of nylon 6 were bundled was obtained.
Sectional area of the ultrafine fibers was measured by the above method, focusing number, the cross-sectional area of the microfine fiber bundle is the same as embodiment 1 either, the ultrafine fibers such as cross-sectional area in the microfine fiber bundle is more than 27 [mu] m ² is carried out Like Example 1, it was not present. The number of ultrafine fiber bundle cross sections existing per unit area of the cross section parallel to the thickness direction is 2200 / mm ^{2 on} average, and most of the ultra fine fiber bundles are not bonded to the polymer elastic body. .

Example 4
One side of the base material for artificial leather obtained in Example 2 was buffed with sandpaper to adjust the thickness to an average thickness of 0.97 mm, and then the other side was buffed with an emery buff machine with sandpaper set. Raising and trimming were performed to form an ultrafine fiber raised surface. Furthermore, using Irgalan Red 2GL (Ciba Specialty Chemicals), it dye | stained by the density | concentration of 4% owf, Then, it brushed and finished the hair and obtained nubuck-like artificial leather. The number of ultrafine fiber bundle cross-sections existing per unit area of the cross-section parallel to the thickness direction measured by the above method is 1950 / mm ^{2 on} average, while having a raised surface that is extremely dense, It had a color development that was not present. The appearance, texture, and surface wear durability were all excellent, and the napped-tone artificial leather had the intended effect of the present invention. The evaluation results are shown in Table 1.

Comparative Example 1
In Example 1, the area ratio of the sea component polymer and the island component polymer of the sea-island fibers constituting the long fiber web was changed to sea / island = 25/75, the average cross-sectional area was 175 μm ^2, and the entanglement by needle punching A base material for artificial leather was prepared under the same conditions as in Example 1 except that needle C having 9 barbs was used instead of needles A and B for the combined treatment. Next, a nubuck-like artificial leather was produced in the same manner as in Example 2 using the obtained artificial leather substrate. The resulting nubuck-like artificial leather had good color developability, but did not satisfy the target level of the present invention in other characteristics. The evaluation results are shown in Table 1.

Comparative Example 2
65 parts of nylon 6 as the island component and 35 parts of low density polyethylene as the sea component were melted in separate extruders. The molten polymer is supplied to a composite spinning die having a number of nozzle holes concentrically arranged to form a cross section in which 50 island component polymers having a uniform cross-sectional area are distributed in the sea component polymer. It discharged from the nozzle hole at ° C. Sea island-type fibers having an average cross-sectional area of 940 μm ² (about 9.8 dtex) were spun by pulling and narrowing the discharged polymer. The obtained sea-island fiber was drawn 3.0 times and crimped, and then cut into a fiber length of 51 mm to obtain a staple. The staple was defibrated with a card and then folded with a cross wrapper to obtain a short fiber web. After the step of further stacking the obtained short fiber webs, a base material for artificial leather was prepared in the same manner as in Example 1. Next, a nubuck-like artificial leather was produced in the same manner as in Example 2 using the obtained artificial leather substrate. The obtained nubuck-like artificial leather had a suede-like appearance with a relatively rough nap, and was completely different from the napped-like artificial leather of Example 2. In addition, the color developability was good, but the surface density was insufficient, the lighting effect was poor, the texture was hard, the pilling resistance was low, and other characteristics were the target level of the present invention. It was not satisfied. The evaluation results are shown in Table 1.

Comparative Example 3
Using nylon 6 as the island component and low density polyethylene as the sea component, the mixture was melted by mixing the sea component and the island component at a ratio of 50/50. The molten polymer was supplied to a spinneret having a large number of nozzle holes arranged concentrically, and was discharged from the nozzle holes at a nozzle temperature of 290 ° C. A sea-island fiber having an average cross-sectional area of 940 μm ² (about 9.5 dtex) was spun by a mixed spinning method in which the discharged polymer was pulled and thinned while converging. The cross section of the sea-island fiber after spinning was in a state where thousands of island components made of nylon 6 were scattered in the sea component made of polyethylene. The obtained sea-island fiber was stretched 3.0 times and crimped, then cut to a fiber length of 51 mm to form staples, which were defibrated with a card and then made into a short fiber web with a cross wrap webber. After the step of further stacking the obtained short fiber webs, a base material for artificial leather was prepared in the same manner as in Example 1. Next, a nubuck-like artificial leather was produced in the same manner as in Example 2 using the obtained artificial leather substrate. The resulting nubuck-like artificial leather surface was generally fine and had a nubuck-like appearance similar to that of Example 2, but it had poor color development, a paper-like hard texture, and other characteristics. The target level of the present invention was not satisfied. The evaluation results are shown in Table 1.

Comparative Example 4
A base material for artificial leather was prepared under the same conditions as in Example 1 except that the entanglement treatment conditions by needle punch were changed as follows.
Prior to the entanglement process in a general needle punching machine, using needles D having a barb with a barb depth of 60 μm located at the same distance from the tip of the blade part, one at each corner of the equilateral triangle cross section. The fiber web was needle punched. Sea-island fiber at a punch depth of 3 barbs penetrating in the thickness direction while conveying a long fiber web with a brush-like belt, with a punch number of 500 punch / cm ² from the opposite side of the brush-like belt They were entangled strongly in the thickness direction. Subsequently, the entanglement process was carried out at 1000 punch / cm < ² > from both sides using the needle A with the needle punching machine similar to Example 1. FIG.
Next, a nubuck-like artificial leather was produced in the same manner as in Example 2 using the obtained artificial leather substrate. The number of ultrafine fiber bundle cross sections present per unit area of the cross section parallel to the thickness direction of the obtained nubuck-like artificial leather was about 800 / mm ^{2 on the} average, but it was 15-50 The portions where the fiber bundles are oriented in the thickness direction, that is, the portions where the number of cross sections of the ultrafine fiber bundles is about 0 to 50 / mm ² existed at intervals of about 100 to 500 μm in the width direction. Therefore, the average of the cross section was about 450 / cm ² . Although the color developability and surface friction durability of the nubuck-like artificial leather were good, the appearance and texture did not satisfy the target level of the present invention. The evaluation results are shown in Table 1.

Example 5
After both surfaces of the artificial leather base material obtained in Example 3 were buffed with sandpaper to adjust the thickness to 0.90 mm and the surface was smoothed, one side was further smoothed with a 160 ° C mirror roll. Processed. This surface was defined as the surface side in the subsequent process. Separately, a 15 μm-thick surface coating layer made of a polyurethane composition mainly composed of polycarbonate-based polyurethane and colored brown with a pigment is formed on a release paper with a texture, and further a polyurethane-based adhesive containing a crosslinking agent thereon An adhesive layer consisting of The obtained two-layer film was bonded to the surface side of the artificial leather substrate via an adhesive layer. After aging treatment for 3 days in an atmosphere of 65 ° C., the release paper was peeled off. Subsequently, using a washer, the surface was subjected to a relaxation treatment for 30 minutes in a 70 ° C. warm water bath containing a surfactant and a softening agent to obtain a silver-tone artificial leather of the present invention. The number of ultrafine fiber bundle cross sections existing per unit area of the cross section of the base material parallel to the thickness direction of the obtained silver-tone artificial leather was 1840 / mm ^{2 on} average, and the density was extremely high. All of the appearance, texture, and adhesive peel strength were extremely good, and it was a silver-tone artificial leather having the intended effect of the present invention. The evaluation results are shown in Table 2.

Comparative Example 5
A base material for artificial leather was prepared under the same conditions as in Example 3 except that the sea-island cross section was changed to a separation-divided fiber, the entanglement processing conditions were changed, and the ultrafinening method was changed.
As the fibers constituting the long-fiber web, sixteen nylon and polyethylene terephthalate (hereinafter referred to as PET) components are alternately laminated in a petal shape, and each component is divided into eight regions having substantially the same cross-sectional area. An exfoliated split type fiber having an average cross-sectional area of 240 μm ² (about 3.0 dtex) having a type cross section was used.
Instead of needle A and needle B, a barb depth of 80 μm and 9 needles E of barbs are used, and a punch depth (about 8 mm) that penetrates from the tip of the needle to the third barb in the thickness direction. ), A needle punching process was performed from both sides with a total number of punches of 1000 punches / cm ² . The film was immersed for 90 seconds in a water bath at a water temperature of 90 ° C. to perform shrinkage treatment, and then water jet treatment at a water pressure of 150 kg / cm ² was performed from both sides without performing press treatment.
Instead of extracting and removing the sea component, the alkali component was treated with an aqueous sodium hydroxide solution to reduce the PET component by about 10%.
When the cross section parallel to the surface and the thickness direction of the obtained base material for artificial leather was observed with an electron microscope, the surface was a long-fiber nonwoven fabric base, but the number of cut fibers was 5 to 10 pieces / mm ^2. In the cross section, 15 to 70 fiber bundles oriented in the thickness direction existed at intervals of about 0.6 to 1.3 mm in the width direction. Subsequently, using the obtained artificial leather substrate, a silver-tone artificial leather was prepared in the same manner as in Example 5. The obtained silver-tone artificial leather had an appearance similar to that obtained in Example 5 at first glance, but the ultrafine fiber bundle present per unit area of the cross section parallel to the thickness direction of the substrate. The average number of cross-sections is 330 / mm ² , which is extremely small, most of the fibers are not divided into ultrafine fibers, and the divided ultrafine fiber bundles are hardly divided. It was adhered to the molecular elastic body. Also, other characteristics did not satisfy the target level of the present invention. The evaluation results are shown in Table 2.

  The nubuck-like artificial leather obtained from the base material for artificial leather of the present invention has a nubuck-like leather-like appearance with a nap like feeling that is extremely dense. In addition, it is excellent in characteristics that have been difficult to combine, such as a texture that is excellent in color developability, a texture that is flexible and swells but has a sense of fulfillment, and a surface friction durability typified by pilling resistance. Further, the silver surface-like artificial leather obtained from the base material for artificial leather of the present invention has an appearance with a natural surface like a natural leather having a high smoothness and a very fine crease. Moreover, it is excellent also in the characteristics which have been difficult to combine conventionally, such as a sense of unity between the base material and the silver surface layer, a soft and swollen texture, and adhesive peel strength. These artificial leathers can be suitably used for applications such as clothing, shoes, bags, furniture, car seats, and various sports gloves such as golf gloves.

Claims (6)

In the base material for artificial leather comprising the nonwoven fabric structure comprising ultrafine fiber bundles and the polymer elastic body contained therein, the following (1) to (4):
(1) The ultrafine fiber bundle is formed of an average of 6 to 150 converged ultrafine fibers,
(2) The cross-sectional area of the ultrafine fibers forming the ultrafine fiber bundle is 27 μm ² or less, and the cross-sectional area of 80% or more of the ultrafine fibers is in the range of 0.9 to 25 μm ² .
(3) The average cross-sectional area of the ultrafine fiber bundle is in the range of 15 to 150 μm ² , and (4) In any cross section parallel to the thickness direction of the nonwoven fabric structure, the cross section of the ultrafine fiber bundle has an average of 1000 to 1000 A base material for artificial leather, which is simultaneously satisfied that it is present in the range of 3000 pieces / mm ² . The base material for artificial leather according to claim 1, wherein the ultrafine fiber bundle is formed of an average of 6 to 90 concentrated ultrafine fibers. The base material for artificial leather according to claim 1 or 2, wherein the polymer elastic body is contained without adhering to the ultrafine fiber bundle. The napped-tone artificial leather in which the napping which consists of an ultrafine fiber was formed in the at least single side | surface of the base material for artificial leather in any one of Claims 1-3. Silver surface-like artificial leather in which a coating layer made of a polymer elastic body is formed on at least one side of the base material for artificial leather according to any one of claims 1 to 3. The base material for artificial leather, wherein the following steps are performed in the order of (a), (b), (c) and (d), or (a), (b), (d) and (c) Manufacturing method.
(A) Melting and spinning sea-island type fibers having an average number of islands of 6 to 150, an average cross-sectional area ratio between the sea and islands of 5:95 to 70:30, and an average cross-sectional area of 30 to 180 μm ² , and cutting this A process for producing a long fiber web by accumulating on a collecting surface in a random orientation state,
(B) A plurality of the above-mentioned long fiber webs are overlapped as necessary, and from both sides, needle punching is performed under the condition that at least one barb penetrates, and the sea-island type fibers are three-dimensionally entangled, A nonwoven fabric structure in which the cross-section of sea-island fibers is present in an average range of 600 to 4000 / mm ² in a cross-section parallel to the thickness direction by densification and / or fixation by shrinkage treatment or heat press treatment as necessary. Manufacturing process,
(C) impregnating the nonwoven fabric structure with a polymer elastic body solution and solidifying the polymer elastic body by a wet method; and (d) extracting a sea component polymer from the sea-island long fibers constituting the nonwoven fabric structure. Or the process which removes by decomposing | disassembling and transforms a sea-island type | mold long fiber into a very thin long fiber bundle.